Mechanical modulator



Jan. 27, 1948. M, FUCHS 2,434,917

MECHANICAL MODULATOR Filed Nov. 6, 1943 2 Sheets-Sheet l wry z.

fj Xc v 14 v p Z1? 15 56 INVENTOR.

MORTON FUCHS Jan. 27, 1948.. FUCHS 2,434,917

MECHANI CAL MODULATOR Filed Nov. 6, 1%43 2 Sheets-Sheet 2 IN VEN TOR. MO/PT 01V FUCHS AT TOHNEY Patented Jan. 27, 1948 TED TATES FATE? vThis invention relates .to modulating systems and more particularly .to modulating systems .adapted "for mechanical operation.

. -It is often desired to modulate.energyvtransmitted with lfixed tone "frequencies, Hfor example, in radidbeacons.

cally moved impedance devicestonu'plediacmsslthe lineyor inseriesitherewith. V

.It is often .di'fficult ;readily to ,provide 1511611 m hanicalmodtilatorsin.acoaxizil'feedline.

It .isxan object .of my invention to (provide a modulator which may readily be used w'ithva-Qeocax'ial.transmission'line.

It .is:aifurther object of my';inventiontoaprovide .a modulator ,for :use with ,a -maxial line, which imay'fl-be vapplied withoutdisturbing the innertcjon- 'ductoroflsaidline. V It is astill further obiecteof ,mylinvention to provide;amodulator,readilyadapted"forgmechanical operatiomsassociated .With a-Qoaxialffeedin line. v v v .According to the principles of my 'linvention, .I make use ,o'La break .or interruption j in the outer or -shield. conductor of "a coaxial transmission line effectively, .to insertan impedanceimseries inthe line. This effective impedance 'ismade variable by a variable impedance meanscoupled effectively in parallel.;across.the efiectlveimpedanoe. (Thus, when the line is used to.delivertpowerlto.alload, variationinthe shunt impedancehsenvestomodulate the'power delivered to the load. The variable, impedancemaytake thefform .ofiaicondenser coupled v across @the .break in they outer conductor, .or between anopen end of the .icondutonatld ground or .v another neutral potential source.

A .better understanding of my invention and the objectsand Qfeaturesthereof may behadib y reference to the jdescriptionof particular embodi- '-ments'there0f.made:w th reference to the-accompanying drawing. in whichz' Fla. .1 is a diagrammatic illustration used jig- .exnlainingthelprlnciplesof m ginvention;

JFig. f2i isia'set of curves-used'in connection with -the. dia ram 0f 1=.ig.. 1,; V v x 1 Fi 3 v11s ,an. euuwalent circuit diagram of 431 6 arramgement ,ofFlg. x1;

3 mg. 4. is a proposed :s'tructural arra. accordance with my invention; a

Fig.5 is'a, modifiadrstructural arrangement embo ied-lnmyinvention; and a. Q' I s Fig. '6 is, azstillufurther structural arrangement embod in omyinvention. o

"In Fig. 1 is shown an arrangement-incorporatgement an tsuchzsystems often take .the form of rotating condensers -.or vother vmerchant 12 of coaxialfline ;l0;is,jsh.0wn. This; line con p'ris es an outeror shield floonductor 11 and a central conductor .12. A source :l3iis coupe'wbetwee'n .-,c0nductor VH and lzfatone end bisection 1'0 and aload M is ;c,odpledfb'etwieen the pentral conductor :I 2 and ,grbund il 1; A ifurther loonn'ection l5 istpmvided .c.onnectiri'g .the end of outer Icontdu'ctor .lil Zadjacentsource SL3 directly to jgro'u'n d '11; .In;accjordance;with this circuit arrangement, it is ,clear -.that-efieotiv1y load I 4 is connected to a, point .on 'thefloutsi'de "of outer .vconductor Ll, as

,shownat T5,. "Thus, theopmen'ded conductor H interrupted Iat the pointB with the load 114 coupled toagpvointlon the outside thereof jprese'nts an impedance :which is effectivjelyin series with load 44. ;A vvariable impedance shown as gonidenser .IB is connected also .between the outer conductor 'and ithe ,neutral tor lgrouncl jpoteritiajl source 1.1,. 'J'I'his oolndensenis efiectivelyjn shunt withkthetimpedanoe presentedbetween,outerilconductortof the line anfderound. Aocordinglmjw varying this impedance Zxc a modulation of {the .:ener y supplied {from J3 to .M {is obtained. \A more neomblete analysis of the operation of the circuitasshown .inflEig. ,1 is given below: tAsf'shownlihkFig. .31, the electrical .lezigthflo'ff c.0- axial line :tllis' 9, the -joliaracteri-stic impedance of ,the, line .is ZOA, theloh-aracteristicoimpoedanoe of the ,dutenconduotor orshieldisZoB. .Theeffeo- .tive impedance tZABtwhich iterminates line [0 ivenJby may :bet'zco'nsidered s a s terminatedein *Za the i-zload warrin .Xc, :thewoltage :aeross-the ;l,oad- 1.4215

modulated. V

in thetfeaturesof ngy imrentlongn mvhiqh alen th 5 g mi z ttpri'ig A;immerse;nraetiealnqnstmetwe arrangement of the circuit, as shown in Fig. 1, is illustrated. In this figure is shown a length of coaxial line 20 provided with an outer conductor 2| and an inner conductor 22. High frequency source 23 is connected between conductors 2| and 22. The outer conductor 2| is broken at 32 providing a gap which serves to introduce an impedance effectively in series withthe load 24 connected between the center conductor and the outer conductor 2| of the line. A conductive support 25 serves to connect the end. of line 20 adjacent source 23 to a source of ground or neutral potential 21. The portion of conductor 2| adjacent load 24 is also connected with ground or neutral potential, as shown at 33 and 34. r The variable impedance is shown as a condenser 26 comprising stator plates 28 and 29 fixed respectively driven at a constant speed by a motor 3|. Rotation of rotor 30 tends continuously to vary the effective shunting impedance of'this condenser between maximumandininimum values. a If the portion of line 2l adjacent source 23 is made slightly less than a quarter wavelength at the operating frequency and the value of the condenser 30 is such that in its lowest capacitive position the outer conductor section is resonant, then the effective impedance in series with load 24 is infinite and no power flows thereto. As the condenser plate is rotated, the impedance reduces to some finite value so that one hundred percent modulation of the energy supplied to load 24 is obtained.

In the structural arrangementshown in Fig. 4, the rotor 38 is not exactly at ground potential since the rotor shaft and support has some electrical length. Actually, it may be preferable to construct the modulating arrangement of two mechanically balanced sections, such as shown in Fi 5. In this figure, the line 40 is provided with an outer conductor 4i and inner conductor 42 coupled to a source 43. A gap 53 is provided and at equi-distant points spaced on opposite sides of gap 53 are provided supports 45 and 56 which serve to connect the two ends of line 40 to ground or other neutral potential source. The lengths of line between the gap and supporting points 45 and 56 are preferably made equal, and in the order of a quarter wavelength long. The variable impedance device comprises a condenser 46 having stator plates 48 and 49 fastened to outer conductor 4| on opposite sides of. gap 53- and a rotor plate 50 rotatably supported between theseplates 48 and 49 and driven at a constant speed by motor It is clear that the two sections of line 4| between the gap 53 and points 45 and 53, respectively, provide two impedance elements efiectively in series with the load. Rotor 40 is accordingly effectively in a neutral plane and therefore will assume the ground or neutral potential. For this reason, no special grounding oithe rotor is required. The condenser tends efiectively to shunt the impedance presented by the two line sections, and is variable between predetermined limits.

In Fig. 6 is shown a structural arrangement substantially similar to Fig. 5 in electrical efiect. In this arrangement, however, the coaxial line 60 is bent in substantially a U-form with a gap 12 provided substantially at the apex of the U. Source 63 supplies energy to load 64 over the two conductors BI, 62 of the coaxial line. A common supporting and ground plate 55 is provided cutting the conductors transversely across the legs of the U. on opposite sides of gap I2 are provided stator plates 68, 69 of condenser 66 and between these plates is supported the rotor 10 of the condenser. This rotor may be rotated at a desired constant speed by a suitable motor 1 I.

While I have illustrated variable condensers as the preferable-forms of modulators used with the system of my invention, it should be clear that this is shown only by way of example. In connec tion with the mechanical modulating arrangement, however, condenser arrangements are generally preferred over inductors since considerably less impedance losses will occur in the capacitive than would occur in the inductive impedances.

It is clear, however, that the principles of my invention need not be confined to mechanical modulating systems of the type illustrated but any type of variable impedance may be provided connected between the conductor sections, as shown, or between a. conductor section and a neutral ground point without departure from my invention. The specific examples and modifications thereof described in this specification are merely illustrations of my invention and should not be considered as limitations on the scope of my invention as set forth in the objects of the invention and the appended claims.

What is claimed is:

1. A modulating system for imparting a modulation to energy supplied from a source to a given load, comprising a section of coaxial transmission line, means for coupling said source between the inner and outer conductors of said transmission line at one end thereof, means for coupling said load between the inner conductor at the other end of said line and the outer conductor at said one end thereof. the outer conductor of said line being provided with a gap intermediate the ends thereof whereby the impedance with respect to ground of theouter surface of said outer line between its ends is effectively in series with said load, variable impedance means effectively bridged across said gap, and means for varying said variable impedance to modulate the energy supplied to said load.

2. A modulating system according to claim 1 wherein said section of coaxial transmission line from said source to said gap is made effectively a quarter of a wavelength long, and. wherein said variable impedance is made variable between an effective short circuit and an effective open circult condition, whereby one hundred percent modulation is substantially obtained.

3. A modulating system for imparting a modulation to energy supplied from a source to a given load, comprising a coaxial transmission line, the outer conductor of said line being provided with a gap, means for coupling said source between the inner and outer conductors of said line 'at one end thereof, means for connecting said outer conductor on the sideofsaid gap toward said source to a neutral potential source, at a predetermined distance from said gap, a load connected to said line between the inner and outer conductors on the end remote from said source. avariable impedance means coupled betweensaid outer conductors, and means for varying said variable impedance in accordance with modu lating signals, to impart modulations to the energy supplied to said load.

4. A' modulating system according to claimji, further comprising means for connecting the end of said'outer conductor immediately beyond said gap on the load end of said conductor tosaid neutral potential source.

5. A modulating system according to claim 3,

further comprising means for coupling said outer conductor on the side of said gap toward said load to said neutral potential source, at said predetermined distance from said gap.

6. A modulating system according to claim 3, wherein said variable impedance comprises a rotary variable condenser, and said means for varying said impedance comprises a drive means for rotating said condenser.

'7. A modulating system comprising a coaxial line having an inner conductor and an outer conductor, the outer conductor being provided with a gap therein, means for connecting said outer conductor to a neutral potential source at equally spaced points on opposite sides of said gap, a high frequency energy source coupled between said inner and outer conductor at one end of the line, a load coupled between said inner and outer conductors at the opposite end of the line, and means for varying the impedance to the energy from said source as supplied to said load, comprising a variable condenser bridged across said gap.

8. A modulating system according to claim 7, wherein said coaxial line is formed in a substantially U shaped section, said gap being provided at the apex of said U.

9. A modulating system according to claim 7,

wherein said coaxial line is formed in a substantially U shaped section, said gap being provided at the apex of said U, said variable condenser comprising stator plates fastened to said outer conductor on opposite sides of said gap, and a rotor plate mounted for rotation between said stator plates, further comprising means for rotating said rotor plate.

10. A modulating system according to claim '7, wherein said variable condenser comprises stator plates fastened to said outer conductors on opposite sides of said gap, and a rotor plate mounted for rotation in spaced relation between said plates, further comprising means for rotating said rotor plate at a predetermined speed.

MORTON FUCHS.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,232,592 Davies Feb. 18, 1941 2,232,591 Davies Feb. 18, 1941 2,228,692 Davies Jan. 14, 1941 2,108,867 Mathieu Feb. 22, 1938 Re. 20,859 Potter Sept. 13, 1938 

